1. The Field of the Invention
The present invention relates to the safe and effective intracorporeal placement of catheters during cannulation of body cavities. More particularly, it concerns illumination of such cavities by a light-emitting fiberoptic cable for placement within a catheter to enable a surgeon to visually observe the catheter tip relative to its organ surroundings.
2. The Background Art
Catheters are well known in the art for injecting fluid into, or withdrawing fluid from, a vein of a patient. Catheters can also be introduced into other cavities or organs of the human body such as the coronary sinus and atria during cardiopulmonary bypass and other open heart surgery procedures. Of current interest are apparatus and methods for quickly and safely placing a flexible catheter within the coronary sinus for infusing a chemical fluid into the heart to temporarily stop and nourish the heart during heart surgery.
It has long been recognized that in order to provide the best surgical conditions during heart surgery, it is necessary to stop the normal operation of the heart and interrupt the blood supply to the heart muscle. A pulsating heart consumes a large amount of oxygen and therefore requires much more energy than an arrested heart. However, even the resting heart needs an oxygen and nutritional supply no keep its muscle cells alive. When the cardiac muscle cells fail to receive enough oxygen the deficiency causes serious damage in the form of perioperative (during or within 24 hours after the surgical procedure) myocardial necrosis (death of the heart tissue). The consequences of myocardial necrosis range from low cardiac blood output to death of the patient. For these and other reasons not specifically discussed, one of the primary goals of myocardial preservation techniques during heart surgery is to stop the heart to thereby reduce myocardial oxygen consumption and thus decrease the risks of oxygen deficiency.
It is well known that stopping the electromechanical work of the heart significantly reduces myocardial oxygen consumption. During heart surgery, the patient's heart can be stopped and the functions thereof taken over by a heart-lung machine. Many methods have been developed to stop the heart during heart surgery to thereby reduce the oxygen and energy requirements of the heart and thus avoid the risk of myocardial necrosis. The most advantageous method used to date is the infusion of a continuous flow of cold cardioplegic fluid to cool and stop the beating of the heart, known as cardioplegia ("heart stop"). Cardioplegic solutions are typically cooled fluids containing potassium, magnesium procaine, or a hypocalcemic composition. In stopping the heart, care must be taken to prevent the heart muscle from continuing to beat without blood being supplied thereto in order to avoid myocardial necrosis.
Cardioplegic fluids for stopping the heart are delivered either directly or indirectly into the coronary arteries or into the coronary sinus (a large vein of the heart through perfusion catheters. Perfusion catheters typically comprise dual tubes coupled together in substantially a parallel alignment. A surgeon grips the catheter by its proximal end and inserts its distal end into the coronary sinus. A selectively inflatable balloon circumscribes the catheter near its distal end and blocks the coronary sinus. One of the tubes is connected at its proximal end to a fluid source and thereby introduces cardioplegic fluid into the coronary sinus. The other tube communicates with the coronary sinus at its distal end and is often connected to a pressure sensor at its proximal end to thereby provide a pressure reading of the coronary sinus. Perfusion (the passage of a fluid over or through the vessels of an organ or tissue) is used to deliver cardioplegia in an antegrade manner (through arteries in the normal direction of blood flow), in a retrograde manner (through veins opposite the normal blood flow direction), or in a combination of antegrade and retrograde delivery.
In retrograde cardioplegia, an old procedure repopularized recently, it is known to insert a balloon catheter through a small incision in the right atrium and then advance the catheter into the coronary sinus. A self inflated or hand inflated balloon stops the normal fluid flow into the right atrium. The cardioplegic solution is then perfused backwards through the coronary veins to the heart, i.e. in a direction reversed to that of normal blood flow. The catheter remains in position throughout the operation in order to periodically readminister the cardioplegic solution. Retrograde cardioplegia is more complicated than antegrade cardioplegia but is often preferred in order to avoid the problems of antegrade delivery, which include: encumbering the limited operative field by the insertion of perfusion catheters directly into the coronary arteries; aortic insufficiency; and nonhomogeneous cooling and cardioplegic maldistribution of areas of the heart downstream from coronary artery obstructions.
It is of life threatening importance that the catheter be properly placed during retrograde cardioplegia. It is suggested that the tip of the catheter be approximately 1 to 2 centimeters from the left atrial appendage. Kit V. Arom, M.D. and Robert W. Emery, M.D., "Retrograde Cardioplegia: Detail for Coronary Sinus Cannulation Technique," 53 Ann. Thorac. Surg., 714-15 (1992). However, the process of properly placing the catheter poses additional risks to the patient. The surgeon must advance the catheter by hand into the coronary sinus to a desired location. If the catheter is under-inserted, the cardioplegic fluid will not be perfused at the desired location and the heart will not receive sufficient oxygenated nutrients, increasing the risk of a failed operation or even myocardial necrosis as discussed above. If the catheter is over-inserted, it may damage the walls of the atrium or the coronary sinus in addition to providing fluid to the wrong location in the organ. This risk arises because the atria and the coronary sinus are made from particularly fragile tissues which tear easily when probed by a catheter.
Control of insertion depth is also important to fully block the coronary sinus after the catheter has been inserted in order to prevent the cardioplegic solution from flowing backward from the coronary sinus into the right atrium. While proper catheter placement is of life-threatening importance in retrograde cardioplegia, it is always important regardless of the particular procedure or operation being performed.
The generally accepted method for confirming proper catheter placement during retrograde cardioplegia has depended upon costly trial and error: the surgeon essentially guides the catheter into the coronary sinus by feel. The surgeon holds a flexible catheter with a stylet in place in the left hand and inserts it into the right atrium anterior to the venous cannula. The surgeon's right hand is placed along the heart's diaphragmatic surface. The surgeon places the index finger at the inferior vena cava and atrioventricular groove junction to locate the catheter tip and gently guide it into the coronary sinus and greater cardiac vein. The surgeon further advances the flexible catheter forward, and manually palpates the inflatable balloon. If the palpations are not felt, it is certain that the catheter is not in place and most likely is in either the right ventricle or inferior vena cava. Arom, "Retrograde Cardioplegia" at 714. The surgeon must then withdraw the catheter and repeat the procedure until proper placement is achieved. This trial and error approach takes precious time away from the rest of the surgery and results in undue risk to the patient's internal body cavities.
In short, the generally accepted method of physically confirming proper catheter placement during retrograde cardioplegia has many disadvantages. One serious disadvantage is that the surgeon cannot see or confirm with absolute certainty that the catheter is in the right place, but must feel to determine proper catheter placement. Not only is this generally accepted method tedious and risky, but it requires the catheters and stylii to be limited to softer material to minimize the risk of injury to the veins and the organ walls. The surgeon is thus caught up in a classic conflict situation: soft structure is needed to protect against puncture, and stiff structure is needed to enable the surgeon to feel for the location of the catheter.
There is thus a great need to minimize the risks of intracorporeal catheter placement, especially for retrograde cardioplegia. U.S. Pat. No. 4,927,412 attempts a solution to this problem by teaching a catheter having a depth control flange coupled to the catheter at a predetermined distance from the catheter tip to prevent the catheter from being over-inserted. The flange comprises a disc made of a soft plastic material which prevents over-insertion when the flange engages the wall of the right atrium while the tip of the catheter protrudes into the coronary sinus. Although this approach does provide protection against over-insertion, the surgeon still cannot see or confirm with absolute certainty that the catheter is in the right place. This approach thus fails to significantly limit the risks of undue wearing or tearing of the coronary sinus and right atrium walls, and still does not preclude over-insertion because the surgeon cannot see the position of the catheter tip relative to its organic surroundings.
Although the industry continues to research methods and devices for assisting in the proper intracorporeal placement of catheters, none of the methods or devices known to applicant involve a self-contained catheter apparatus which enables the surgeon to actually see the position of the catheter tip relative to the delicate walls of the body cavities and organs. It is clear that there is a need for a catheter positioning apparatus and method which not only allows greater flexibility in choosing among the use of softer or stiffer catheter materials, but which also allows the surgeon to actually see and observe the position of the catheter tip relative to its organic surroundings.